gas pipes 118 natural gas 99 gasworks industry 71 pipelines 53 history 47 natural gas energy sources 36 material testing 33 more ... corrosion of material 27 gas fuels 22 material defects 22 power engineering 19 consumption 17 supply 17 corrosion protection 15 fuels (transport) 14 wandering currents 13 preservation of material 13 technical standards 11 cleaning 11 biofuels 10 steel 10 gases 10 town gas 10 calculations 10 safety 9 underground structures 9 production 9 fatigue of material 9 measurement 8 flow measurement 8 less ...